1. Field of the Invention
This invention is generally related to power amplifiers and, more particularly, to a system for increasing overall efficiency of a power amplifier by varying operating voltage applied to a power amplifier based upon the output power level of the power amplifier.
2. Related Art
In personal communications devices such as cellular telephones, there is a trend toward minimizing size and weight. The size and weight are, however, contingent upon the size and weight of the various components that make up the personal communications device. In short, the smaller the various components of the personal communications devices, the smaller the size and overall weight of the personal communications device itself. Many personal communications devices have an overall size and weight which is, to a large degree, dominated by the size and weight of the battery which provides a supply voltage to the personal communications device. This is generally due to the fact that consumers want a personal communications device to have a prolonged operating time during usage.
As operating time requirements and power consumption of the personal communications device during operations increases, the size of the battery required to perform under these circumstances will also increase. Thus, where current or power consumption of the personal communications devices can be reduced; or the size of components can be reduced; the size of the battery can also be reduced. Alternatively, where the size of the battery remains constant, the operating time of the personal communications devices can be increased.
In typical personal communications devices such as, for example, wireless communication devices, efficiency of the device is optimized at maximum power output without regard to whether or not maximum power output is actually needed. Thus, as the power output of a typical wireless communications device, for example, drops below the maximum power (Max Power) output level, the efficiency of the wireless communications device also drops. This does not help to prolong the supply battery voltage and thus works to limit the operation time to the device.
The invention provides a system for improving the efficiency of a power amplifier. Briefly described, in architecture, the system can be implemented as follows: a power amplifier unit and a power management unit are provided. An operating voltage is applied to the power amplifier unit. The power management unit monitors the current drawn by the power amplifier unit and generates a control signal based upon the measured current. The operating voltage applied to the power amplifier unit is adjusted based upon the control signal. Adjustment to the operating voltage may be made via the power management unit or via an external regulator unit.
The invention can also be viewed as providing a method for applying an operating voltage to a power amplifier unit. In this regard, the method can be broadly summarized by the following steps: An operating voltage Vbb is applied to a power amplifier unit 120. The current drawn by the power amplifier unit is then monitored and the current flow is measured. A current flow signal is generated and output based upon the measured current flow. The current flow signal is then received by a controller that generates a control signal based upon the current flow signal. The control signal is then output to a voltage regulator, which then adjusts the operating voltage applied to the power amplifier unit based upon the control signal.
Other systems, methods, features, and advantages of the invention will be or become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.